1. Field of the Invention
This invention concerns a method for formation of a miniature block pattern with high aspect ratio on the bottom part of the step on a surface having a step, and in particular concerns a method for formation of the upper magnetic pole layer of a thin film magnetic head capable of high recording densities and having an upper pole which is a miniature block pattern with high aspect ratio.
2. Background Information
Composite heads which integrate a magnetoresistance effect head for reproduction with an inductive head for recording are generally employed as the thin film magnetic heads incorporated into hard disk devices for computers. As exemplified in FIG. 6, in these composite heads, after forming a magnetoresistance effect head 9 provided with a magnetoresistance effect element film 6 between upper and lower shield layers 4, 8 separated by reproduction gap layers 5, 7 on the surface of a substrate (slider) 2 covered with a nonmagnetic undercoat 3, the inductive head 17 is formed with the upper shield layer 8 as a common pole (the lower magnetic pole layer).
This inductive head 17 is obtained by forming by layering in order, on the common pole 8, multiple component layers including a recording gap layer 10, an insulating layer 11 to serve as the coil base, thin film coil layers 12, 14, insulating layers 13, 15 covering said coil layers 12, 14, and an upper magnetic pole layer having a pole part 16a and yoke part 16b. 
In order to accommodate higher linear recording densities on hard disks, multiple component coil layers are used in order to generate a stronger magnetic field in the recording gap, as shown in FIG. 6. Due to the configuration characteristic of said thin film inductive head, on the surface on which the upper magnetic pole layer 16 is formed by layering, a comparatively large step occurs between the exposed surface Sp of the gap layer on which the pole part 16a is formed by layering, and the upper surface Sy of the coil insulating layer 15 on which the yoke part 16b is formed by layering, as shown in FIG. 7.
In order to form, on a surface with this step, an upper magnetic pole layer 16 with the prescribed film thickness, ordinarily a plated base film is first deposited, and on top of this photoresist is applied using a spin-coating method; said resist is exposed and developed to pattern it with the planar shape of the upper magnetic pole layer 16, and using the patterned resist as a frame, magnetic material is usually grown to a prescribed film thickness on top of the exposed plated base film by an electroplating method.
It is required that the pole part of the upper magnetic pole layer of recording heads be formed with high precision with a core width of less than 1 xcexcm, in order to conform to the narrow track widths of reproduction heads using newly developed giant magnetoresistance effect films, represented by spin valve films.
However, the upper magnetic pole layer must have a certain film thickness in order to secure a sufficient saturation flux density, but in forming a frame using the aforementioned single-layer photoresist, it is difficult to achieve submicron-order precision due to spreading and other phenomena during exposure and development.
An apparatus and method of forming an upper magnetic pole layer of a thin film magnetic head having a pole part and a yoke part is disclosed. In one embodiment, the method includes forming by layering an approximately flat lower magnetic pole layer, a magnetic gap layer, at least one thin film coil layer, and an insulating layer covering the at least one coil layer, of a plated base film, on a surface of a substrate. Next, a first resist layer of approximately uniform film thickness over an entirety of the plated base film is formed by vacuum thin film formation. A relatively thin second resist layer is formed on top of the first resist layer. The second resist layer is patterned in a planar shape of the upper magnetic pole layer. The first resist layer is patterned by anisotropic dry etching using the patterned second resist layer as a mask. The upper magnetic pole layer is formed by wet plating on an exposed region of the plated base film using the patterned first resist layer as a frame.